This invention relates to an impact testing device and more particularly to an impact testing device wherein the sample material to be tested is in a stressed condition.
In the design of pipelines, it is necessary to determine the resistance of the pipeline steel to cracking and bursting. Since the pipeline in its operational condition will be under stress from whatever it is carrying, any testing of the pipe for cracking and bursting should ideally be done with the pipeline under stress. Ordinarily, such testing is done through a burst test procedure which requires pressurizing a one thousand foot section of actual pipe with a small charge being detonated to force a crack. A burst test destroys a lot of expensive pipe and can very easily result in an expenditure of approximately $750,000 for each burst test. Impact testing equipment such as the Charpy or Battelle drop-weight tear test machines were designed to measure the energy absorbed during the fracture of free-standing unstressed samples. The Charpy and Battelle machines were designed to eliminate the need for the expensive burst tests but the Charpy and Battelle machines are unable to simulate actual conditions since the material being tested is unstressed.
Therefore, it is a principal object of the invention to provide an impact testing device wherein the material to be tested is pre-stressed.
Another object of the invention is to provide a pre-stressed impact testing device including means to insure that the sample will be extended during impact fracture to eliminate loss of the pre-stressed load.
A further object of the invention is to provide an impact testing device which simulates actual operational conditions.
A further object of the invention is to provide an impact testing device which enables the determination of the energy absorbed during fracture of metal samples under pre-stressed conditions which simulate actual operational experience.
These and other objects will be apparent to those skilled in the art.